MRI features in foetal microtia

Background: Atresia of the external auditory canal is positively correlated with the difficulty and success rate of operation after birth. At present, ultrasound screening often obtains images of body position, placenta and amniotic fluid, and the detection rate is low. Moreover, it is unable to evaluate whether the external auditory canal shows atresia. Methods: We retrospectively conducted MRI features of 9 cases those were diagnosed foetal microtia from May. 2019 to Oct. 2020. Results: Nine cases of microtia foetus were analysed: male, five cases; female, four cases; right ear, five cases; left ear, four cases; and degree I, one case (bilateral external auditory canal is shown); degree II, eight cases (affected external auditory canal is not shown, six cases of normal external auditory canal shown, two cases of normal external auditory canal not shown). All parturients underwent amniocentesis full exon gene detection, of which the results were negative. The magnetic resonance imaging (MRI) features of microtia, included abnormal external ear morphology, disappearance of normal structure, mass-like and small piece-like soft tissue shadow and equal signal on T2-weighted (T2W) imaging. The upper and lower diameters were significantly smaller than that of the normal side. The MRI features of external auditory canal atresia included disappearance of T2W linear high signal shadow in the temporal bone scale. Conclusions: Foetal MRI can diagnose microtia and evaluate atresia of the external auditory canal.

Case of oculo-auriculo-vertebral spectrum: rare clinical features

A 2-month-old boy presented to us with bilateral microtia, left lower motor neuron facial palsy, micrognathia, hemivertebra, bifid rib, bifid thumb and absent/hypoplastic right-sided depressor anguli oris. He had bilateral external auditory canal atresia, although response to loud sound was present. Brain stem evoked response audiometry (BERA) was advised at 3 months of age. Karyotype was normal. We diagnosed him as a case of oculo-auriculo-vertebral spectrum. Child was discharged on request by the family with the plan for bone-anchored hearing aid after BERA and plan for pinna and ear canal reconstruction at a later age but child did not come for any follow-up visit. On telephonic enquiry, it was found that he is thriving well but has developmental delay including speech delay. We conclude that children presenting with external ear abnormalities should be screened for multiple congenital anomalies so that a multidisciplinary approach to management can be planned.

3D Printing of a BAHA Protective Cap

Mechanical feedback is one of the most common difficulties encountered when fitting hearing aids for toddlers and young children. We described the use of 3D printing to tailor a protective cap for a toddler with bilateral microtia/canal atresia to facilitate bone-anchoring hearing aid use.

Administration of All-Trans Retinoic Acid to Pregnant Sows Improves the Developmental Defects of Hoxa1−/− Fetal Pigs

Hoxa1 mutation adversely affect fetal pig development, but whether all-trans retinoic acid (ATRA) administration to Hoxa1+/− pregnant sows can improve Hoxa1−/− fetal pig development defects has not been reported. A total of 24 healthy Hoxa1+/− sows were mated with a healthy Hoxa1+/− boar and randomly assigned to one control group and nine experiment groups. ATRA was orally administered to pregnant sows at the doses of 0, 4, 5, or 6 mg/kg maternal body weight on 12, 13, and 14 days post coitum (dpc), respectively, and a total of 146 live piglets were delivered including 37 Hoxa1−/− piglets and 109 non-Hoxa1−/− piglets. Results indicated that Hoxa1−/− piglets delivered by sows in control group had bilateral microtia, canal atresia and ear's internal defects, and had lower birth liveweight and external ear score than non-Hoxa1−/− neonatal piglets (P < 0.05). Maternal administration with ATRA can effectively correct the development defects of Hoxa1−/− fetal pigs, Hoxa1−/− neonatal piglets delivered by sows administered ATRA at a dose of 4 mg/kg body weight on 14 dpc had higher birth liveweight (P > 0.05) and higher scores of external ear (P < 0.05) compared to Hoxa1−/− neonatal piglets from the control group, but had no significantly difference in terms of birth liveweight and external ear integrity than non-Hoxa1−/− piglets from the control group (P > 0.05). The time of ATRA administration significantly affected Hoxa1−/− fetal development (P < 0.05). Administration of ATRA to Hoxa1+/− pregnant sows at 4 mg/kg body weight on 14 dpc can effectively improve the birth liveweight and ear defects of Hoxa1−/− piglets.

Anatomy and Development of the Mammalian External Auditory Canal: Implications for Understanding Canal Disease and Deformity

The mammalian ear is made up of three parts (the outer, middle, and inner ear), which work together to transmit sound waves into neuronal signals perceived by our auditory cortex as sound. This review focuses on the often-neglected outer ear, specifically the external auditory meatus (EAM), or ear canal. Within our complex hearing pathway, the ear canal is responsible for funneling sound waves toward the tympanic membrane (ear drum) and into the middle ear, and as such is a physical link between the tympanic membrane and the outside world. Unique anatomical adaptations, such as its migrating epithelium and cerumen glands, equip the ear canal for its function as both a conduit and a cul-de-sac. Defects in development, or later blockages in the canal, lead to congenital or acquired conductive hearing loss. Recent studies have built on decades-old knowledge of ear canal development and suggest a novel multi-stage, complex and integrated system of development, helping to explain the mechanisms underlying congenital canal atresia and stenosis. Here we review our current understanding of ear canal development; how this biological lumen is made; what determines its location; and how its structure is maintained throughout life. Together this knowledge allows clinical questions to be approached from a developmental biology perspective.